1. Field of Invention
The invention relates generally to optical communications networks and in particular to distribution of information to multiple optical network elements.
2. Description of Related Art
Optical communications networks utilize a variety of network elements to transmit information from sender to receiver. The network elements may be geographically distributed over a wide area and typically include one or more processors for executing network element software. One difficulty in managing communications networks is the distribution of software to multiple network elements.
One approach to distributing software is a static mechanism where copies of the software image are transmitted to one of the network elements referred to as a gateway network element (GNE) and the other network elements obtain the software image from the GNE. Multiple copies of the software image are provided from a software source to the GNE for retrieval by each requesting network element (RNE). Such a distribution technique is depicted in FIG. 6 which illustrates a download to RNEs 1, 2, 4, and 6–10. As shown in FIG. 6, this technique requires multiple (i.e., 8) streams of the software image to be distributed to the RNEs. This approach has several disadvantages including manual operation, high bandwidth requirements and the consumption of storage space on the GNE that is otherwise needed for logs, swap space, and persistent storage of network parameters.
For next-generation network elements the consumption of GNE storage space is particularly disadvantageous because each network element is a distributed processing machine containing many different types of circuit packs. Each circuit pack may support a particular set of telecommunications services such as ESCON, or ETHERNET or SONET/SDH. Each circuit pack, being similar to a processor element in a distributed processing machine, requires a software image of its own to execute. The total software image for such a network element can be on the order of 100 to 200 Mbytes, which is a significant amount of storage space for a network element. Software image size is much bigger for new generation network elements because new generation network elements, both optical and data network elements, have multiple interface cards.
Furthermore, the manual nature of this conventional software image download process is not only inefficient but also can cause unexpected results when not performed in a specific sequence. The unexpected results could include rebooting/crashing of network elements, particularly those network elements experiencing a heavy packet forwarding load.
An alternative to the static RNE-uploads-from-GNE approach in an on-the-fly distribution mechanism such as a multicast distribution mechanism based on a distribution tree. This technique requires a complex multicast routing protocol to be in place so that a download tree can be setup automatically. Multicast is un-reliable and clients/receivers join multicast session asynchronously. As a result, multicast sessions are carousel-based where the GNE continuously multicasts the software image in a cycle. This consumes resources of the GNE particularly as the size of the software image increases.